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```Research and Development Laboratories

of the
Portland Cement Association

RESEARCH DEPARTMENT

Bulletin 68

Porosity of Hardened
Portland Cement Pastes

L. E, COPELAND

and
J. C. HAYES

March, 1956

JOURNAL OF THE AMERICAN CONCRETE INSTITUTE

18263 W. McNichols Rd., Detroit 19, Michigan
February, 1956; Proceedings Vol. 52, p. 633

Title No. 52-39

Porosity of Hardened Portland Cement Pastes

By L. E. COPELANDt and J. C. HAYES*

■p

SYNOPSIS

Continued study of the properties of hardened poitland cement pastes
has provided information which makes it possible to estimate porosity of
pastes more precisely than is possible by using the original equations of Powers
and Brownyard. The total pore volume of hardened pastes is 0.99 w € .
Capillary pore volume is the difference between total pore volume and pore
volume characteristic of the gel in hardened pastes.

The pore volume of the gel is assumed to be the lowest pore volume that
has been observed in hardened pastes. The paste with the lowest pore
volume was made with w /c = 0.235 and cured for 11 years. The gel porosity
calculated for this paste is 0.26. The average Dumber of layers of water
molecules on the surface of this saturated gel is 2.38.

INTRODUCTION

Definitions of symbols

a

€

€
k

Vt

I'c

= nonevaporable water per gram of
cement in a completely hydrated paste

= weight of cement

= density of a saturated hardened paste

= porosity of hardened paste

= ratio of V m to u\

= capillary pore volume in hardened

paste

= gel pore volume in hardened paste

= total pore volume in hardened paste

= specific volume of pure water

= specific volume of cement

= specific volume of hydration products

v t = apparent specific volume of the total

water
V = partial specific volume of water

V m = weight of water required to form an

in a hardened paste
= volume of paste

= weight of evaporable water in the
hardened paste
Wn = weight of nonevaporable water in the

hardened paste
Wl = weight of total water in the hardened

paste

V

General relationships

The fact that a hardened portland cement paste that is saturated with water
can lose all of its evaporable water with only a slight change in volume im-
plies that the hardened paste is porous. A study of relationships between

the properties and porosities of hardened pa- >s led Powers and Brownyard 1
to conclude that there are two classes of pores: (1) gel pores— small pores

s

between the gel particles, and (2) capillary pores— pores larger than gel pore:
which exist between aggregates of gel particles.

♦Received by the Institute Jan. 27, 1955. Title No. 52-39 is a part of copyrighted Jocbnai oftiir America*
Concrete Institute. V. 27. No. 6, Feb. IQ5G. Pmceedmps V. 52. Separate pnnto are available at 35 cento
each. DiscuHion (copies in triplicate) should reach the Institute not later than June 1, l9ob. Address 1820J W .

McNichols Rd., Detroit 19. Mich. . . 4 n . . ...

tSesior Research Chemist, Research and Development Division, Portland Cement Assn Chicago II.
tSenior Research Chemist, Zonolite Co., Chicago, 111. (formerly Assistant Research Chemist. Portland

Cement Assn.).

633

634 JOURNAL OF THE AMERICAN CONCRETE INSTITUTE February 1956

Some of »li« physical properties of a hardened paste, the permeability to

sv -, , r example, depend upon the total porosity; other properties, such as

ompressive strength and resistance to freezing, are related to the capillary

osity. Therefore, an accurate equation for capillary porosity is necessary

,. ,„ isely the effect of capillary and gel porosities upon the prop-

rti< - of tl pasti

Some of the details of t lie Powers and Brownyard model have been changed

result of continued research. We have found thai their equation for

ilating capillary porosity gives negative values in a few instance con-

uently, the prol of computing I lie i sity from certain readily measured

, ri . I fche p.i- has been studied further so as to understand the cause
i i _ itive r< ultfi and to obtain a e accurate equation.

The nation for ilculating capillary pore volume, i>, given by Powei
id B wnyard. is

= - : l + ■

■

< 1 1

where ii i ginal net* water content of the fresh paste, vo n is the non-

tent of the saturated, hardened paste, v t is the minimum
tpj rent specific volume of the total water that can exist in

urated : • n is th zje n ber of layere of water in the gel por<

,,i amount of watei necessary i<» form a monolayer on
1 to tin le v • ' content ot ihe paste.

I Hi.- olume ol watei in hardened paste us the difference

ii the -luii- <ii the i '< ai I the volume «•! the cement n i imams

led I thi Jit "t \\ both fi and chemically combined, in the

P l I

i

i

I ilume of th< at* I be ■ afr t change <ti olume ot i hi

P h n ' _• in i h< weight ot watei it main- at a constant

1 1 1 • le water con tent

h of 1 1 Kq I) and t d 1 hal i po ii y "I

(»1\ -ma i ti mated from i h«- pante* availabh

1. I. In di • that the partial -p ifi<

I I l| I p ; ' ' : !• .

1 1 I pn Foi calculi \uti \»> n I I < « >1 al

■ j I eqi i I " 1 1 i ot I hi olution b< Id

.' < d. II lijinc can he - iniated I roil

d tl lun ' l.< er i

It i he < na j i j 1 h< -ai • manner I m paf

•I »ov

V

tl i

i

POROSITY OF HARDENED PORTLAND CEMENT PASTE

63

which contain no capillary pores. The capillary pore volume is simply thi
difference between the total and gel pore volumes.

EXPERIMENTAL PROCEDURES

Materials

Paste were prepared from five different cements covering a wine ranji
>ment compositions. The computed potential compound comp ion
i he cement ire gi\ en in Ta ble I .

Preparation of samples

of

oi

The pa let u ed in t hi> investigation were, with the exceptions n< ed be!
mi ed in a vacuum by the method described in a pn ious papei Sinc<
p i ho prepared were free from air* hubbies, theif water «. tents ould
determined accurately from simple drying or ignition procedun

The paste- were cured under wain .t 73 F, in closed gla mold*

Some ol the results con idered here were obtain I u i pa prepared i

othei project Although curing pro lun varied, i e was exi I

include only the results obtained on saturated pastes lh
eparated into three groups:

Group I
i evidence

a I I 1 1 1 1 \ I e - 1

These specimens were prepared for permeability udi

i

rin

thai some leaching ol lime i m! alkali occurred duri

(iroup I The e pastes were prepared to determine th<
the ipecifii surface ; 1 1 m I the nonevaporable - f t

nonevaporal »le w a t er a h possible

P

icn i rai i

Group 4 \ eries of specimens were prepared in 1940 in ac< ith tl

p dure used for autoclave tests of ceme Tin pen ured ii

inoisl Ho i I duri nil t he first 21 hi and under \\ ah a l ', I until ana, I

nd of II years Water ement ratios ranged from n 2 i to 0.2o bv '
These pastes were not va mm mixed, I -hl\ broli -un i <

i

specimens appi kred wet, indicating that thi pecimei i. I

leaehi occurred during the 11 -year curing period This showri

paring the chemical analysis oi the cured paste with thi d

I lie cement

TABLE 1— PROPERTIES OF CEMENTS USED IN POROSITY INVESTIGATION

l«

s i

nt

S«l frill I'T fcS

S|
v oltn

ea cm

1

1 ■_•■ 1 1

(

1 -

1.^7

s
1
1

IS
IS

1H4KJ
L84X)

\ 1 9
115

n

U7

ill

1 w

I

n 10

r, m

i
II 9

■

'

i!

1

1

I t

I 7

1 ■ -

_"'

1

. VI

-

■
I

36

JOURNAL OF THE AMERICAN CONCRETE INSTITUTE

February 1 956

Analytical methods

The total water content, w h of saturated, hardened pastes prepared by the
acuum mixinu procedures was calculated directly from the ignition loss it

]M00 F. oi the pa>te. A correction for the original ignition loss of the cement

Vi (When the pastes contained air voids, the total water content wa

und from the sum of noiievaporable water and evaporable water, the latter

ing de rmined by the procedure described by Powers and Brownyard.-'
The ■'. tisiti< dp, oi the saturated pastes prepared by the vacuum mixin
proa dure were determined by a specific gravity balance. This determination
w m . upon th( sample before it was crushed and dried for other tests.
I p S : group 3, the density determination was performed on -amp]

which v i _ undated to eliminate voids. The grinding was done in a con-
trolled aln I cabinet where the air Was Saturated with water and h

Nonevaporable water in the mples, to*, was determined from the ignition
I, t 19001 oi mples dried in an evacuated desiccator connected to a trap

■ ; bv dry i< i md alcohol. 5

I i \ J, n\ and total water content oi i uum-mixed, saturated

km I is i Bible I calculate original water content, < mming thai

i ii volume chai g< :urs duri i the hydration period. Lei c and Wi

icp | the wi in of the cemenl and total water, respectively, in the

I lei I i I Ken

■

i +

•

hen ■ the specifii olu i of the cemenl and apparent specific

ilu i the t .1 \ er, resp tivelj and d, is the paste densit}

1 '

Ii tip

IX

■ rhang< luring I h< hydrat ion period

. i . •. ii and i I he specific ' olunru emi<

I Mi I •: _' id

—

'

\

\

UllU

I . gi> in b ' be right-hand meml i

I i i that tl wi • ratio u dil] d< ined.

the p • wen • timated from ■'> i adsorption m< ..

uiemei s. Tin iioil!lt> <»t ;il< ui-

TABLE 2— RELATIVE VAPOR PRES-
SURES OVER SATURATED SOLUTIONS
OF COMPOUNDS USED FOR RELA-
TIVE VAPOR PRESSURE CONTROL

I

H

Mi

1ir«

i i

i \,t four di it n it i i vapoi

prcsHin en d< ine<i h m<

n t hi • - 'i1 iii' f ■ •' amp i

d I to i he now

ite, suspended from nh tig

lash jack I ...< h j

uaH'd ;»' the jnti lud

ii i ;i ii 1 1 rf-n

POROSITY OF HARDENED PORTLAND CEMENT PASTES 637

sel containing a saturated solution of a pure compound. The four compounds
and the relative vapor pressures over their saturated solutions are listed in
Table 2.

The two parameters, Y m and C, of the BET adsorption equation 6 were

calculated from adsorption data. Y m is the amount of water necessary to form
a complete monolayer over the surface, and C is related to the average heat of

DISCUSSION
Total pore volume in hardened pastes

Powers and Brownyard determined the specific volume of the solid phases
in hardened pastes by a helium-displacement method and obtained the volume
of pores from the difference between over-all volume and volume of the solid

hases. Then from the mass of water in saturated samples they concluded
that water in gel pores had a smaller specific volume than water in capillary
pores. The difference between the specific volume of gel and capillary water
complicated the calculation of porosity of pastes. In an investigation reported
in another paper we found, by a water-displacement method, that partial
Bpecific volume of gel water is equal to that of capillary water in saturated

astes.- This simplifies determination of the total pore volume in hardened

pastes.

The pores of a saturated paste are filled with a solution of soluble cement
constituents, principally alkalies, in chemically tree water. We cannot de-
termine directly the density of this solution, but we have determined that
partial specific volume of chemically free water in pastes made from certain
low-alkali cements is (MM). It is not likely that variations in cement com-
position, including variations in alkali content, will affect this value appre-
ciably. Consequently, we can use it to approximate closely the volume of the
solution in the pores of hardened pastes by calculating the volume occupied by
chemically free water in saturated paste. This approximation has been applied
to solutions of KOH and XaOH in the range of concentrations to be expecti
in hardened pastes. The difference between approximated volume and true
volume of the solution is less than O.o percent. Even if the concentration of
alkali in the evaporable water were twice the probable highest concentration.
the error would be below 1 percent. We believe, therefore, that the error in
pore volume associated with this approximation is less than 0.5 percent. The
evaporable water content is assumed to be equal to the chemically free water
content of hardened pastes.

In other words, within 0.5 percent, the total pore volume, />,, of a hardened
paste is equal to the weight of evaporable water in the saturated paste multi-
plied by 0.99, i.e..

p t = 0.99 it-, = 0.99(u>« - Wn)

(5)

^mce the water gained by the paste during the curing period is given by

wt - »•„ = 0.254 w„ (Ref. 2)

638

JOURNAL OF THE AMERICAN CONCRETE INSTITUTE

February 1956

Cement

No.

it

15754

0.310

15756

. 348

15758

0.310

15761

o 317

15703

374

TABLE 3— MEAN k VALUES FOR it follows that

VARIOUS CEMENTS Vt = 0.99(w„ - 74(1/ )

Gel pore volume

Powers and Brownyard concluded

that the framework of a hardened
paste was a gel which possessed its
own characteristic porosity. They
had evidence that the gel pores could
hold a quantity of water equal to 4V m ,
or the equivalent, 4/ ,,. The term n of Eq. (1) was thus assigned the value
of 4 by Powers and Brownyard.

When the procedure for determining w n was revised,'' it became necessary
to investigate again the relationship between V m and «*„. The later work
hows that V m is proportional to w n in pastes made from cements with normal
( - nd C 3 S contents, but 1\ may not be exactly proportional to w, in paste
n (< from cements with high (" S contents. Since the departure from pro-
portionality is small, even if real, we shall ignore it, and use the values of ft
reporl ed in Table 3 for different cements. These values are different from those
reported by Powers and Brownyard because of the difference in the method
of determining w n . The relationship between V m and w n will be discussed in
moo detail in another paper.
The proportionality of Y m to w n implies that the specific surface of the hy-

Iration products is a constant and is independent of the extent of hydration
of the cement in the paste. Apparently, gel particles do not grow larger as
hydration proceeds; but new particles, similar in size to those firsl formed, are

iroduced. It seem- reasonable to suppose that a mechanism thai produces
gel particles of fairly uniform size should also produce a fairly uniform mode
of packing these particle-: consequently, the gel would possess a characteristic
porosity.

Thi minimum value of the ratio w e /V m for hardened pastes is a measure of
gel porosity lor pore* of saturated hardened paste are filled with evaporable

water; and surface area, which is proportional to 1 „,. is due to colloidal hy-
Iration products comprising the gel. The lowest value of "v/1 .., found for
] • investigated in this work is 2.38. We have not been aide to establish
the minimum i due, although the proportionality between Y m and w, implie
that a gel porosity corresponding to w e , V m ^ 1 musl exist.

The general results we have obtained in attempt ing to determine a minimum
value for w, \'„ are illustrated by the following consideration:
Since

</•.

r

«n

I \>

- 1

(I

it follows thai if a lower limit
also exist . In a saturated

for w, 1 gists, a lower limit for "', u musl
w t w n is related to the original water-cement

itio, w, ' . by ihe equation

POROSITY OF HARDENED PORTLAND CEMENT PASTES

639

Fig. 1 relationship

for pastes of cement 15754

w
at two — - levels

GO

5.0

4.0

W t

W

3.0

n

2.0

1.0

w?=a/J77

-. O. I64G

0.2

4

0.6

W
C

Wt

ll'n

ir„ c

Wn/C

+ 0.264 ... .(7;

From Eq. (7) we should expect then thai the ratio w, w for saturated,
hardened pastes having the same ir r would lie on a straight line when plotted
against w /c. The intercept of this line at w a <=o -Tumid be 0.254, and the
slope I (n\ c). Fig. I is a plot of two sets of data. These data were obtained
on past< at ages up to 11 years. The point- are close to the theoretical lim

md show no break, indicating that the minimum > r > "'• has i ot be< n r< :hed.

The lowest values of ir, u\ were reached after I 1 years; it is aoi likely that
values appreciably lower than these will ever be reached. It will probably b
necessary to deduce the minimum values of u\ ir, and w, 1 from othei types
of measurements.

The porosity, e. of a hardened paste containing neither unhydrated cemenl
nor capillary pores is

O.99i0.

i ■

w t \

€ =

Vh

( 1 + i)"~

4- 0.99 M ' f r u

{>

0.99*

+

I

w here v h is the specific volume of the hydration products and a is I he maximum
value of w n c. Porosities calculated from Eq. (8) with w, l. =2.38 rang*
from 0.2b to 0.28 for the cement- studied here. These porosities are close to
that characteristic of a close-packed system of uniformly sized spheres, 0.26.

Inequality of particle size in a close-packed system could lead to porosities

640 JOURNAL OF THE AMERICAN CONCRETE INSTITUTE February 1956

smaller than 0.2<, and consequently to ratios of wJX m smaller than 2.38.
We believe, however, that particle size distribution in gels is narrow; thus,
gel porosity should not fall much below 0.2G.

Accordingly, the best estimation of p now possible is given by

p„ = 0.99 X 2MV m = 0.99 X 2.38*u>„ = 2.36/. " ,. (9)

Capillary pore volume in hardened pastes

( pillary pnn- in hardened pastes are larger than gel pores. They exist
as spaci thai have not been filled by gel particles and may be completely
surrounded by gel. The volume of the capillary pores, p e , is the difference
ietween the total pore volume of the hardened paste and the gel-pore volunw
It is calculated by combining Eq. (5) and (9).

p c = p t - p = 0.99 [w t - (1 + 2.38A-),r,] ()

or

p c = 0.99 [w - (0.746 4- 2Mk)w n ]

Porosity of hardened pastes

The ons given above relate pore volume to nonevaporable water and

total water in urated, hardened pastes. Usually these quantities are ex-
prc ed as fractions oi cement content of the pastes. Porosity is the pore

volume in unit volume of paste and can be calculated from w, C and ir, c by
multiplying pore volume per unit weight of cement by amount of cement in a

mit volume of p • The equations for total and capillary porosity are:

Pt

e = '— = 0.99

Wn

c

J 1 + —

(11)

I = °

- ( I + 2.38/

1 ^>

12

wh - the density and 1 is the volume of the paste.

REFERENCES

1. Pov I < and Brownyard, T I. Siu«lu- of tin Physical PropertM >f Harden*

I Cement P id Joi rnal, Pm V. 13: Oct. 1946, pp. 101-132 Nov. 1946,

Pi 2 I I'm- pp. h" m Jan. 1947, pp. 549-604; ] 1947, pp. 669-712; Mar.
pp. sr 380 \|- 1947, pp ! 1-992.

2. i. I.. E., unpublisl ed ma ipt. •

3. Pow< 'J' ( I opeland, L. I If . J. ( and Mum, If. M., "Permeabilitj of
P !' \< I Journal, Nov. L954, Proe. V. 51, pp.

\ Pow< 3, T I md Brow I, T. I., op pp. 2> .

5. - ope] I, !.. I ind H • .1 ( iSTM Bulletii No. 194, Dec. 1953, p 7".

8 En i, 1*. If and Teller, I /< at of A icon Cht ical >'<<<
\ ■ v p 309.

For such discussion of this paper as may develop please see Part 2,
December 1956 Journal. In Proceedings V. 52 discussion immediately
follows the June 1956 Journal pages.

Research Department

Research and Development Division

of the

Portland Cement Association

Bulletin 2

Bulletin 1— "Estimation of Phase Composition of Clinker in the System 3CaO

Si0 2 -2CaO Si0 2 -3CaO Al20 3 -4Ca0 Ah0 3 Fe 2 3 at Clinkering Temper-
atures," by L. A. Dahl, May, 1939.

Reprinted from Rock Products, 41, No. 9, 48; No. 10, 46; No. 11, 42; No. 12. 44
(1938); 42, No. 1. 68; No. 2, 46; No. 4, 50 (1939).

-"The Bleeding of Portland Cement Paste, Mortar and Concrete Treated
as a Special Case of Sedimentation," by T. C. Powers; with an appendix
by L. A. Dahl; July, 1939.

-"Rate of Sedimentation: I. Nonflocculated Suspensions of Uniform
Spheres; II. Suspensions of Uniform-Size Angular Particles; III.
Concentrated Flocculated Suspensions of Powders"; by Harold H.
Steinour, October, 1944.

Bulletin 4— "Further Studies of the Bleeding of Portland Cement Paste," by Harold

H. Steinour, December, 1945. "

Bulletin 3

Bulletin 5

Bulletin 5A

Bulletin 6

Bulletin 7

Bulletin

Bulletin 9

Bulletin 10

Bulletin 11

"A Working Hypothesis for Further Studies of Frost Resistance of
Concrete," by T. C. Powers, February, 1945.

ceedings, 41, 245 (1945).

Supplement to Bulletin 5; Discussion of the paper "A Working Hy-
pothesis for Further Studies of Frost Resistance of Concrete," bj

T. C. Powers; discussion by: Ruth D. Terzaghi, Douglas McHenby,
H. W. Brewer, A. R. Collins, and Author; March, 1946.

1945); Proceedings, 41, 272-1 1945).

"Dynamic Testing of Pavements," by Gerald Pickett, April, 1945.

41, 473 (1945).

"Equations for Computing Elastic Constants from Flexural and Tor-
sional Resonant Frequencies of Vibration of Prisms and Cylinders,"

by Gerald Pickett, September, 1945.

discussion, 864.

"Flexural Vibration of Unrestrained Cylinders and Disks," by Gerald
Pickett, December, 1945.

"Should Portland Cement Be Dispersed?" by T. C. Powers. February,
1946.

ceedmgs, 42, 117 (1946).

"Interpretation of Phase Diagrams of Ternary Systems," by L. A. Dahl,
March, 1946.

"Shrinkage Stresses in Concrete: Part 1— Shrinkage or Swelling ,
Its Effect upon Displacements and Stresses in Slabs and Beams of
Homogeneous, Isotropic, Elastic Material; Part 2— Application of the
Theory Presented in Part 1 to Experimental Results"; by Gerald
Pickett, March, 1946.

Reprinted from Journal of the Amer n Concrete Institute (January and February.
1946); Proceeding*. 42. 165. 361 (1946).

Bulletin 12

Bulletin 13

Bulletin 14

Bulletin 15

Bulletin 16

Bulletin 17

Bulletin 18

Bulletin 19

Bulletin 20

Bulletin 21

Bulletin 22

Bulletin 2.t

Bulletin 24

Bulletin 25

Bulletin 26

"The Influence of Gypsum on the Hydration and Properties of Portland
Cement Pastes," by William Lerch, March, 1946.

"Tests of Concretes Containing Air-Entraining Portland Cements or
Air-Entraining Materials Added to Batch at Mixer," by H. F. Gonner-
man, April, 1947.

Reprinted from Journal of the American Concrete Institute (June, 1944 I; Proceedings,
40, 477 (1944 . also supplementary data and analysis, reprinted from Supplement
(November, 1<44 ; Proceedings, 40, 508-1 (1944).

"An Explanation of the Titration Values Obtained in the Merriman
Sugar-Solubility Test for Portland Cement," by William Lerch,
March, 1947.

"The Camera Lucida Method for Measuring Air Voids in Hardened
Concrete," by George J. Verbe< k, May, 1947.

43, 1025 (1947).

"Development and Study of Apparatus and Methods for the Determina-
tion of the Air Content of Fresh Concrete," by Carl A. Menzel, May,
1947.

Reprinted from Journal of the American Concrete Institute (May, 1947 ; Proceedings,
43, 1053 (1947).

"The Problem of Proportioning Portland Cement Raw Mixtures:
Part I — A General View of the Problem; Part II — Mathematical Study
of the Problem; Part III — Application to Typical Processes; Part IV —
Direct Control of Potential Composition' 1 ; by L. A. Dahi, June, 1947.

Reprinted from Rock Products, 50, No. 1, 109; No. 2, 107; Xo. 3. 92; Xo. 4. 122 (1947).

The System CaO-Si0 2 -H20 and the Hydration of the Calcium Sili-
cates," by Harold H. Steinour, June, 1947.

"Procedures for Determining the Air Content of Freshly-Mixed Con-
crete by the Rolling and Pressure Methods/' by Carl A. Mi.n/el,

June, 1947.

Reprinted from Proceedings, American Society far Testing Mater < 47, 833 (1947).

The Effect of Change in Moisture-Content on the Creep of Concrete
under a Sustained Load," Gerald Pickett, July, 1947.

ceedings, 38, 333 (1942

Effect of Gypsum Content and Other Factors on Shrinkage of Concrete
Prisms," by Gerald I kett, October, 1947.

Reprinted fn Journal of the American Concrete Institute (October, 1947;; Pro-
ceedings, 44, 149 1 i.

"Studies of the Physical Properties of Hardened Portland Cement
Paste," by T. C. Powers and T. L. Brownyahb, March, 1948.

I • Tinted from Journal of th* < U InetituU October-] embei 1946;

January-April, 1947 / ?*, 43, 101, 249, 46! 669 845,933 L947).

"Effect of Carbon Black and Black Iron Oxide on Air Content and Dura-
bility of Concrete/ 1 In omaf (i. Taylor, Mmv. 1948.

Reprinted from Journal of the A tie h U Vpril. 1948 Pro />.

44 • 13 1948 -

'Effect of Entrained Air on Concretes Made with So-Called 'Sand-
Graver Aggregates," by Pai i Kliegeb, November, 1948.

Rep from J f the Amer . Concrete Institute (Oct 1948); Pro-

ceeding 45. 149 I'M

A Discussion of Cement Hydration in Relation to the Curing of Con-
crete/* bj I I Powers, August, 1948.

Repri i from Pr< JL , Rest h Board, 27, 178 (1947).

"Long-Time Study of Cement Performance in Concrete." This bulletin

compr - foui install men the report of this investigation, by 1. R

M< Mil] v I. L. Tyler, \Y. I . Hansen, William Leech, I I i >bd I
L S. Brow \. August, 1948.

from J Febi uai -May, 1 ;

P 44. J41 7J : ^77 )•

Bulletin 27 — "Determination of the Air Content of Mortars by the Pressure Method,"

by Thomas G. Taylor, February, 1949.

Bulletin 28 — "A Polarographic Method for the Direct Determination of Aluminum

Oxide in Portland Cement," bv C. L. Ford and Lorrayne Le Mar,
April, 1949.

-"The Nonevaporable Water Content of Hardened Portland-Cement
Paste — Its Significance for Concrete Research and Its Methods of
Determination," by T. C. Powers, June, 1949.

Bulletin 30 — "Long-Time Study of Cement Performance in Concrete — Chapter 5.

Concrete Exposed to Sulfate Soils," by F. R, McMillan, T. E. Stanton,
I. L. Tyler and \Y. C. Hansen, December, 1949.

Bulletin 31-

Bulletin 29

"Studies of Some Methods of Avoiding the Expansion and Pattern
Cracking Associated with the Alkali-Aggregate Reaction," by William
Lerch, February, 1950.

for Testing Materials (1950).

Bulletin 32 — "Long-Time Study of Cement Performance in Concrete — Chapter 6.

The Heats of Hydration of the Cements," by George J. Verbeck and
Cecil W. Foster, October, 1949.

"The Air Requirement of Frost-Resistant Concrete," by T. C. Powers;
discussion bv T. F. Willis.

"Aqueous Cementitious Systems Containing Lime and Alumina,"

by Harold H. Steinour, February, 1951.

Bulletin U

Bulletin

Bulletin 35

Bulletin 36

Bulletin 37

Bulletin 38

"Linear Traverse Technique for Measurement of Air in Hardened
Concrete," by L. S. Brown and C. U. I'ilrson, February, 1951.

ings. 47, 117 (1951).

"Soniscope Tests Concrete Structures," bv E. A. Whitehurst, February,
1951.

ceedings 47, 433 (1951).

"Dilatometer Method for Determination of Thermal Coefficient of
Expansion of Fine and Coarse Aggregate," by Georoe J. Verbeck and

Werner E. Hass, September, 1951.

"Long-Time Studv of Cement Performance in Concrete — Chapter 7.
New York Test Road," by F. H. Jackson and I. L. Tyler, October, 1951.

Reprinted from Journal of the American Concrete Institute (June. 1951 ' ; Proceeding*
47, 773 (1951).

Bulletin 39

. t

Bulletin 40

Bulletin 41

Bulletin 42

Changes in Characteristics of Portland Cement as Exhibited by Lab-
oratory Tests Over the Period 1904 to 1950," by H. F. Gonnebman and

William Lerch.

Materials.

"Studies of the Effect of Entrained Air on the Strength and Dura-
bility of Concretes Made with Various Maximum Sizes of Aggregate,"

by Paul Klieger.

Reprinted from Proceedings of the Highway Research Board. 31. 177 (19 •-'

"Effect of Settlement of Concrete on Results of Pull-Out Bond Tests,"
by Carl A. Menzel, November, 1952.

"An Investigation of Bond Anchorage and Related Factors in Rein-
forced Concrete Beams," by Carl A. Menzel and William M U ood-
N'ovember, 1952.

Bulletin

Bulletin 44

Bulletin 45

Bulletin 46

4 'Ten Year Report on the Long-Time Study of Cement Performance
in Concrete/' by Advisory Committee of the Long-Time Study of Cement
Performance in Concrete, R. F. Blanks, Chairman.

49, BO! (1953).

"The Reactions and Thermochemistry of Cement Hydration at Ordi-
nary Temperature/' by Harold H. Steinour.

Sept. 1952.

"Investigations of the Hydration Expansion Characteristics of Portland
Cement/' bv H. R Goxnermax, Wm. Lerch, and Thomas M. Whiteside
June, 1953.

"Theory of Volume Changes in Hardened Portland Cement
During Freezing/' by T. C. Powers and R. A. Helmvth.

Paste

Bulletin 47 — "The Determination of Non-Evaporable Water in Hardened Portland

Cement Paste/' by L. E. Copeland and John C. Hayes.

Bulletin 48 — "The Heats of Hydration of Tricalcium Silicate and beta-Dicalcium

Silicate," by Stephen Bri water, J. C. Hayes and \Y. E. Habs.

Bulletin 49 — "Void Spacing as a Basis for Producing Air-Entrained Concrete/'

by T. C. Powers.

50. 741 (1954).

Bulletin 49A — Discussion of the paper "Void Spacing as a Basis for Producing Air-
Entrained Concrete/ 1 by J. E. Backstrom, R. \Y. Burrows, V. E. Wolk-
odoff and Author, T. C. Powers,

Reprinted from Journal of the American Concrete Institute (Dec. Part 2 1954); Pro-
ceeding, 50, 760-1 (1954).

Bulletin 50— "The Hydrates of Magnesium Perchlorate/' by L. E. Copeland and R.

H. Bragg.

Reprinted from The Journal of Physical Chi misi // 58. 1075 (1954).

Bulletin 51 — "Determination of Sodium and Potassium Oxides in Portland Cement

Raw Materials and Mixtures, and Similar Silicates by Flame Photom-
etry/' I C. L. Ford.

Bulletin 52— "Self Desiccation in Portland Cement Pastes/' by L. E. Copeland and

R. H. Bragg.

Bulletin 55— "Permeability of Portland Cement Pastes/' by T.C. Powers, L E. Cope-
land, J. C. Hayes and II. MM an v

Reprinted from Journal of the Am an Concrete Institute, f November. 1954); Pro-
ceedings, 51. 2>i5 (1955).

Bulletin 54 — "Some Observations on the Mechanics of Alkali-Aggregate Reaction/ 1

by L. S. Brown.

Bulletin 55

An Interpretation of Published Researches on the Alkali-Aggregate
Reaction: Part 1— The Chemical Reactions and Mechanism of Expan-
sion; Part 2 — A Hypothesis Concerning Safe and Unsafe Reactions
with Reactive Silica in Concrete/' by T. C. Powers and II H. Steinoub.

Reprinted from Journal of the American Concrete h te (February and April. 1955);

Proceedings, 51 197, 785 (1955

Bulletin 56

. *

Comparison of Results of Three Methods for Determining Young's
Modulus of Elasticity of Concrete/' by U E, Philleo.

'> M 4ol 1

Bulletin 57 — "Osmotic Studies and Hypothesis Concerning Alkali-Aggregate Re-
action/* by <h;orge J. Vekbec k and Charles Gramlkh.

Bulletin 58 — "Basic Considerations Pertaining to Freezing and Thawing Tests," b

T. (\ PoWBBfl

Bulletin 59— "New Study on Reactions in Burning Cement Raw Materials/'

L. A. I.) A HI*

Hepnn ted from Rock Product*, 58, No. 5 7! N 102 Wo 7^

Bulletin 60 "Long-Time Study of Cement Performance in Concrete Chapter ,J

Correlation of the Results of Laboratory Tests v\ i t h Field Performam
Under Natural Freezing and Thawing Conditions," \ I II J v. k \

Keprintfd from Journal o '•• \ Concrete! *r

52, 100 (1956).

Bulletin 61— "A Method for the Determination of the ( menl Content <»f Plastic

Concrete/' h\ \\ < . IIimi itrul li \ W in Id

Bulletin 62 — "Investigation of the Franke Method ol Determining I i Calcilll

Hydroxide and Free Calcium Oxide," by I I Pri "i phen Bri

\ \ i i it and I ) L, Kani it".

Reprinted froin Inalytirat ( <mj ( IX) -

Bulletin 6 A — "Ifydniullc Pressure in Concrete," l>\ I I Po* » »

Reprinted from P i td I I m* I H ' '

Bulletin 64— "The Freezing and Thawing Test," I I ( Po*

gut* U'\ I 'iition r> ■

Bulletin 65 — "The Stoichiometrv of the Hydration of Intalci mi Sitlcal »i Boom

Temperature: 1 — Hydration In a Ball Mill II — llvdratinn in a Pa

Form," bj Stephen Bri \ \ • er, L I i II! II I

Bulletin 66 — "Effect of \ugregate on Shrinkage of Concrete and Hypotln ncern

ing Shrinkage, "bj Gerai d Ph kett.

Reprinted fi om J I »*<

i'j 52, p >8I 195*5

Bulletin 67 — "Observations on the Resistance ol Concrete to h r zing and I haw-
ing/' l>\ Ih bert Woods [ncludi dis< ion I. E. Baci
\\ \\ Hi \i\ii )w s, and aul hor'a cIohuj

IN j printed f n >m / ■ ' m

SI, 345 I 9 • ■ . I >i l'7 i 5 1

Bulletin 6H— "Porosity of Hardened Portland Cement Paetee," I I

I: inted from i '

i 'i ■ ,i,

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